Bind the DataSource into JNDI, and then specify its
location in the jta-data-source or
non-jta-data-source element of the
JPA XML format (depending on
whether the DataSource is managed by JTA), or in the
openjpa.ConnectionFactoryName property.

Specify the full class name of the DataSource
implementation in the openjpa.ConnectionDriverName property in place of a JDBC
driver. In this configuration OpenJPA will instantiate an instance of the named
class via reflection. It will then configure the DataSource
with the properties in the
openjpa.ConnectionProperties setting.

The features of OpenJPA's own DataSource can
also be used with third-party implementations. OpenJPA layers on top of the
third-party DataSource to provide the extra
functionality. To configure these features use the
openjpa.ConnectionFactoryProperties property described
in the previous section.

2.1.
Managed and XA DataSources

Certain application servers automatically enlist their DataSource
s in global transactions. When this is the case, OpenJPA should not
attempt to commit the underlying connection, leaving JDBC transaction completion
to the application server. To notify OpenJPA that your third-party
DataSource is managed by the application server, use the
jta-data-source element of your
persistence.xml file or set the
openjpa.ConnectionFactoryMode property to
managed.

Note that OpenJPA can only use managed DataSources when
it is also integrating with the application server's managed transactions. Also
note that all XA DataSources are enlisted, and you must
set this property when using any XA DataSource.

When using a managed DataSource, you should also
configure a second unmanaged DataSource that OpenJPA can
use to perform tasks that are independent of the global transaction. The most
common of these tasks is updating the sequence table OpenJPA uses to generate
unique primary key values for your datastore identity objects. Configure the
second DataSource using the non-jta-data-source
persistence.xml element, or OpenJPA's various
"2" connection properties, such as openjpa.ConnectionFactory2Name
or openjpa.Connection2DriverName. These
properties are outlined in Chapter 2,
Configuration
.